The invention relates to a bearing assembly for mounting a bearing journal of rotatable roll, drum (for example drying cylinder) or the like, specifically having the features that permit longitudinal expansion or contraction of a mounted roll and in particular to the means permitting the bearing housing for the roll to shift longitudinally of the roll. The bearing assembly includes a bearing journal of a rotatable roll supported by a spherical bearing element and the spherical bearing element is held in a bearing housing. The bearing journal of the rotatable roll is fixed in the direction of the longitudinal axis of the bearing assembly within the bearing housing. The bearing housing is in turn supported to a base which is, in turn, supported on a foundation. The invention is concerned with adjustment in the position of the bearing housing with reference to the base. The invention relates both to bearing assemblies for a roll or drum of which the bearing journals are rotatable together with the roll body, and to bearing assemblies for a roll or pressing unit through which a stationary yoke with stationary bearing journals extends; this is, for example, a controlled deflection roll or an elongated nip pressing unit.
To be more precise: the invention relates to a bearing assembly in which the bearing journal is fixed in the axial direction in the bearing housing and in which the bearing housing is connected with the aid of axial guide elements to a base. The latter is fastened on a machine frame or foundation; under certain circumstances, it may also be fastened on a swivel lever. The axial guide elements allow the rotating roll body and/or the stationary yoke to expand in the longitudinal direction during operation, the bearing journal shifting together with the bearing housing in the longitudinal direction. This arrangement makes it possible that--in the case of a rotatable bearing journal--the rolling-contact bearing is fixed axially in the bearing housing, that is to say it is not displaceable axially in the latter. In the case of a stationary bearing journal, the latter is likewise fixed axially in the bearing housing. Thus, in both cases, it is possible to dispense with sliding surfaces, which on the one hand would have to be suitable for transferring great forces (for example pressing forces) and on the other hand would have to be suitable for the said axial displacement.
A preferred field of application of the invention is that of pressing apparatuses for a running web. Such a pressing apparatus may, for example, be part of a paper making machine and serve for dewatering or smoothing the paper web to be produced. Such an apparatus is preferably composed of a first rotatable pressing roll, the bearing journals of which are rotatable together with the roll body, and of a second pressing roll or a pressing unit, through which a stationary yoke with stationary bearing journals extends. In these cases, an internal loading device is provided on the stationary yoke. Concerned here are, for example, hydrostatic supporting elements, which transfer the pressing force from the stationary yoke onto the roll shell, or a shoe, which transfers the pressing force from the stationary yoke via a flexible pressing shell or via a flexible pressing band onto the first pressing roll. To be more precise: preferably concerned is a pressing apparatus with a closed system of forces; this means that the forces resulting from the pressing force are not introduced into a machine framework, foundation or the like, but are transferred with the aid of tension elements directly from the first pressing roll onto the second pressing roll or the said pressing unit. These tension elements preferably act directly on the mutually opposite bearing blocks; see, for example, Patent Application P 41 10 205.2.
U.S. Pat. No. 4,272,317 describes a pressing apparatus, in which a closed system of forces is likewise formed with the aid of tension bars. The upper pressing roll of this pressing apparatus is suspended with the aid of axial guide elements on a base. These axial guide elements thus need only to bear the dead weight of the complete pressing apparatus; they do not serve for transferring the pressing forces. Specifically, the following is provided there: at one roll end, the bearing housing is suspended by means of two links on a base, which for its part is fastened on the underside of a framework. At the other roll end, the bearing housing is suspended by means of a pivot on a similar base. A disadvantage of this design is that it can be used only if the roll (or the complete pressing apparatus) can be suspended on the underside of a framework; this is so since, in all other arrangements, for example in a standing arrangement, this design would be unstable.
So-called knife-edge bearings are also known. Here, the bearing housing rests on rolling-contact bodies which for their part are supported on the upper side of a base. A disadvantage of this design is that it is suitable exclusively for a standing arrangement. Moreover, the force transfer from the bearing housing to the base must only ever take place in the direction from top to bottom (not in the reverse direction), and the level of the transferable force is relatively low.